An Optical System and Method for Detecting Rotation of an Object

1. A system for detecting rotation of a knob in an apparatus, the system comprising: a shaft having a predetermined length and a first end and a second end, the second end having an oblique reflective surface defined thereon, the first end fixedly attached to the knob; a rotation body containing the shaft, the rotation body having a receptacle to accommodate the second end of the shaft, the oblique reflective surface of the second end being exposed; an optical module on an integrated circuit substrate and optically coupled to the rotation body, the optical module detecting light irradiance from the exposed oblique reflective surface, the optical module including, a solid state light source; a plurality of photo detectors each of which generate an electrical signal upon exposure to at least a threshold amount of light, arranged about the light source on a plane in at least two pairs, each pair defining a first and a second direction parallel to the plane, the first and the second directions being perpendicular to each other; wherein the oblique reflective surface generates an asymmetric irradiance profile as light from the solid-state light source is reflected back to the plurality of photo detectors; wherein each pair of photo detectors generates a first electrical signal and a second electrical signal in response to the irradiance profile of the oblique reflective surface; and the optical module detecting a change in the asymmetric irradiance profile from the oblique reflective surface of the shaft as the knob is rotated; wherein the asymmetric irradiance profile is arranged within a boundary at least partially covered by the plurality of photo detectors; wherein the knob is equipped with a spring, the knob being movable between a rest position and a moved position, the moved position being attained in response to the application of a vertical force upon the knob, the spring returning the knob to the rest position upon release of the vertical force; and wherein the moved position of the knob is at least one of the following: a pulled position, a pushed position; furthermore upon the knob attaining the pressed position, the irradiance profile of the oblique reflective surface has a higher intensity in the pressed position than that of the rest position; and furthermore upon the knob attaining the pulled position, the irradiance profile of the oblique reflective surface has a lower intensity in the pulled position than that of the rest position.

2. The system as recited in claim 1 , wherein an axis of rotation of the shaft is substantially centered relative to the solid state light source.

3. The system as recited in claim 2 , wherein the degree of shaft rotation is in the range of about 0° to about 360°.

4. The system as recited in claim 3 , wherein the angle of the oblique reflective surface relative to a direction in which light is emitted from the solid state light source is about 45°.

5. The system as recited in claim 2 , wherein the angle of the oblique reflective surface relative to a direction in which light is emitted from the solid state light source is in the range of about 0° and 90°.

6. The system as recited in claim 2 , wherein the angle of the oblique reflective surface relative to a direction in which light is emitted from the solid state light source is in the range of about 22° and 68°.

7. The system as recited in claim 2 , wherein the angle of the oblique reflective surface relative to a direction in which light is emitted from the solid state light source is in the range of about 5° to 30°.

8. The system as recited in claim 2 wherein the oblique reflective surface is formed on the second end of the shaft by one of the following: directly polishing the second end of the shaft to a predetermined angle, grinding the second end of the shaft to a predetermined angle and attaching a reflective surface to the second end.

9. The system as recited in claim 1 , wherein each pair of photo detectors is coupled to a differential circuit, each differential circuit receiving the first electrical signal and the second electrical signal, and in response, generating non-zero differential output signals, Sx and Sy, representing an X-coordinate and Y-coordinate, respectively.

10. The system as recited in claim 9 , wherein the non-zero differential output signals define a vector having an angle, the angle of the vector representing the degree of shaft rotation.

11. The system as recited in claim 9 , wherein the degree of shaft rotation is indicated by arrangement of the following Signals: Sx >0, Sy>0 represents the Angle θ at about 0° to about 90°, Sx<0, Sy>0 represents the Angle θ at about 90° to about 180°, Sx<0, Sy<0 represents the Angle θ at about 180° to 270°, and Sx>0, Sy<0 represents the Angle θ a about 270° to about 360°.

12. The system as recited in claim 1 , wherein the intensity of the irradiance profile is measured by at least one of the following: monitoring the common-mode signal of all at least two photo detectors; and monitoring the derivative of the common-mode signal with respect to time, as the knob is depressed.

13. A system for detecting a degree of rotation of a motor shaft, the motor shaft having an exposed oblique reflective surface defined thereon, the system comprising: a rotation body accommodating the exposed oblique reflective surface of the motor shaft, an integrated circuit optical module optically coupled to the rotation body, the optical module containing a solid state light source and a plurality of photo detectors arranged to detect an asymmetric irradiance profile as light from the solid-state light source is reflected back from the exposed oblique reflective surface to the plurality of photo detectors, the plurality of photo detectors generating an output representing a vector having a magnitude and an angle, the vector representing the degree of rotation of the motor shaft; a circuit for calculating the degree of rotation with respect to time thereby measuring the speed of the motor shaft; and a circuit for calculating a vertical displacement of the motor shaft from a stopped state to a running state thereby measuring an amount of vertical play of the motor shaft.

14. A method for detecting the degree of rotation of a shaft in an apparatus, the shaft having a predetermined length and a first end and a second end, the second end having an oblique reflective surface defined thereon, the method comprising: inserting the second end of the shaft into a rotation body having a receptacle to accommodate the second end of the shaft, optically coupling an integrated circuit optical module to the rotation body, the optical module containing a solid state light source and a plurality of photo detectors; detecting an asymmetric irradiance profile as light from the solid-state light source is reflected back from the exposed oblique reflective surface to the plurality of photo detectors, generating an output from the plurality of photo detectors, the output representing a vector having a magnitude and an angle; determining the degree of rotation of the shaft from the vector representation; calculating the degree of rotation with respect to time thereby measuring the speed of the shaft; and calculating a vertical displacement of the shaft from a stopped state to a running state thereby measuring an amount of vertical play of the shaft.